Atoms, Molecules and Stoichiometry

Crystals of copper(II) nitrate are prepared by adding an excess of malachite to nitric acid.

The formula of malachite is $\text{Cu(OH)}_2\cdot\text{CuCO}_3$. ($M_{\text{r}} = 221.0$)

$12.0\text{ g}$ of malachite is added to $30.0\text{ cm}^3$ of $1.50\text{ mol dm}^{-3}$ nitric acid.

Which mass of malachite is left unreacted when the reaction is complete?

Options

A   $2.05\text{ g}$
B   $2.49\text{ g}$
C   $7.03\text{ g}$
D   $9.51\text{ g}$

An excess of zinc reacts with $x\text{ cm}^3$ of $2.00\text{ mol dm}^{-3}$ hydrochloric acid.

The gas produced is dried and collected.

The gas occupies $1.534\text{ dm}^3$ at $101\text{ }000\text{ Pa}$ and $293\text{ K}$.

The gas produced behaves as an ideal gas.

What is the value of $x$?

Options

A   $31.8\text{ cm}^3$
B   $34.7\text{ cm}^3$
C   $63.6\text{ cm}^3$
D   $69.4\text{ cm}^3$

An aqueous solution of hydrogen peroxide is placed in a flask and decomposes, as shown.

$$2\text{H}_2\text{O}_2(\text{aq}) \rightarrow 2\text{H}_2\text{O}(\text{l}) + \text{O}_2(\text{g})$$

The total volume of oxygen gas evolved is $180\text{ cm}^3$ after 90 seconds, measured under room conditions.

The rate of the reaction is calculated using the equation shown.

$$\text{rate} = \frac{\text{change in moles of } \text{H}_2\text{O}_2}{\text{time}}$$

What is the average rate of the reaction, measured in $\text{mol min}^{-1}$, over the duration of the experiment?

Options

A   $8.33 \times 10^{-5}$
B   $1.67 \times 10^{-4}$
C   0.0050
D   0.010

Two nitrates decompose on heating according to the equations shown.

$$2\text{Pb(NO}_3)_2(\text{s}) \rightarrow 2\text{PbO}(\text{s}) + 4\text{NO}_2(\text{g}) + \text{O}_2(\text{g})$$ $$2\text{NH}_4\text{NO}_3(\text{s}) \rightarrow 2\text{N}_2(\text{g}) + \text{O}_2(\text{g}) + 4\text{H}_2\text{O}(\text{l})$$

One mole of each nitrate is heated separately. The gas produced in each reaction is bubbled through $\text{NaOH}(\text{aq})$.

The volume of any gas that does not react with $\text{NaOH}(\text{aq})$ is then collected and measured.

Which nitrate:

• shows the greater percentage loss in mass
• produces the greater volume of gas collected?

Options

The diagram shows the structure of progesterone.

Which statement about progesterone is correct?

Options

A   One molecule contains four chiral carbon atoms only; the molecular formula is $\text{C}_{19}\text{H}_{26}\text{O}_2$.
B   One molecule contains four chiral carbon atoms only; the molecular formula is $\text{C}_{21}\text{H}_{30}\text{O}_2$.
C   One molecule contains six chiral carbon atoms; the molecular formula is $\text{C}_{19}\text{H}_{26}\text{O}_2$.
D   One molecule contains six chiral carbon atoms; the molecular formula is $\text{C}_{21}\text{H}_{30}\text{O}_2$.

$\text{ICl}_3$ reacts with water in a redox reaction.

$$v\text{ICl}_3 + w\text{H}_2\text{O} \rightarrow x\text{HCl} + y\text{HI} + z\text{HIO}_3 + z\text{HClO}_3$$

What are the numbers $v$, $x$ and $z$ in the correctly balanced equation?

Options

In the diagram, curve X was obtained by measuring the volume of oxygen produced during the decomposition of $100 \text{ cm}^3$ of $1.0 \text{ mol dm}^{-3}$ hydrogen peroxide. A catalyst of manganese(IV) oxide was used.

Which alteration to the original experimental conditions would produce curve Y?

Options

A   adding more manganese(IV) oxide
B   adding some $0.1 \text{ mol dm}^{-3}$ hydrogen peroxide
C   adding water
D   raising the temperature

P is a compound that burns in an excess of oxygen to give carbon dioxide and water only.

$2.20\text{ g}$ of P contains $1.20\text{ g}$ of carbon and $0.20\text{ g}$ of hydrogen.

When P is added to a solution of sodium carbonate, bubbles of gas are seen.

What is P?

Options

A   $\text{CH}_3\text{CHO}$
B   $\text{CH}_3\text{CO}_2\text{H}$
C   $\text{CH}_3\text{COCH}_2\text{CH}_2\text{OH}$
D   $\text{CH}_3\text{CH}_2\text{CH}_2\text{CO}_2\text{H}$

$50 \text{ cm}^3$ of $1.0 \text{ mol dm}^{-3}$ $\text{H}_2\text{SO}_4$ is added to $100 \text{ cm}^3$ of $1.0 \text{ mol dm}^{-3}$ $\text{NaOH}$ in an insulated vessel.

Both solutions are at a temperature of $20\text{ }^{\circ}\text{C}$ before mixing. After mixing, the temperature rises and the highest temperature reached is $29\text{ }^{\circ}\text{C}$.

Assume that:

• all the energy released in the reaction goes into raising the temperature of the aqueous reaction mixture
• the specific heat capacity of the mixture is $4.2 \text{ J cm}^{-3} \text{ K}^{-1}$.

What is the value of the enthalpy of neutralisation determined from this experiment?

Options

A   $-113.4 \text{ kJ mol}^{-1}$
B   $-56.7 \text{ kJ mol}^{-1}$
C   $-37.8 \text{ kJ mol}^{-1}$
D   $-18.9 \text{ kJ mol}^{-1}$

Barium dithionate, $\text{BaS}_2\text{O}_6\cdot2\text{H}_2\text{O}$, is soluble in water.

$\text{S}_2\text{O}_6^{2-}$ ions slowly decompose in acidic solution.

$$\text{S}_2\text{O}_6^{2-}(\text{aq}) \rightarrow \text{SO}_2(\text{g}) + \text{SO}_4^{2-}(\text{aq})$$

$3.513\text{ g}$ of $\text{BaS}_2\text{O}_6\cdot2\text{H}_2\text{O}$ is dissolved in water in a $100 \text{ cm}^3$ volumetric flask and the solution made up to the mark with $\text{HCl}(\text{aq})$.

At time $x \text{ min}$, a white precipitate of mass $0.661\text{ g}$ is present in the flask.

What is the concentration of $\text{BaS}_2\text{O}_6$ in the volumetric flask at time $x \text{ min}$?

Options

A   $0.0077 \text{ mol dm}^{-3}$
B   $0.0090 \text{ mol dm}^{-3}$
C   $0.077 \text{ mol dm}^{-3}$
D   $0.090 \text{ mol dm}^{-3}$